Ecology
Population Ecology
Part 2
Predicting Populations
Sex and
the
Single
Guppy
2
Natural Selection
• This includes describing how organisms respond
to the environment and how organisms are
distributed.
– Events that occur in the framework of ecological time
(minutes, months, years) translate into effects over
the longer scale of evolutionary time (decades,
centuries, millennia, and longer).
3
Natural Selection
4
Natural Processes
5
Finch Beak Size or Shape
6
Modes of Selection
http://gregladen.com/blog/2007/01/the-modes-of-natural-selection/
7
Modes of Selection
Disruptive- produces a bimodal curve as the extreme
traits are favored
Stabilizing-reduces variance
over time as the traits move
closer to the mean
Directional-favors a
phenotypic trait (selected by
the environment)
Scenario
These photographs show the
same location on Captiva
Island following Hurricane
Charley.
What would happen to a
population of birds who
derive their diets from the
tree tops? The population had
a wide range of beak sizes.
What would happen to the
population gene pool over
time if the new environment
favored smaller beaks? Over
time, which beak would be
most represented in the
population of birds?
9
Selection Diagrams
A
B
C
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Beak Selection After Hurricane
11
Biogeography & Distribution of Species
• Serves as a starting point to understanding
limits on distribution of species
Species absent
because
Yes
Yes
Dispersal
limits
distribution?
Yes
No
No
No
Biogeography & Distribution of Species
• Serves as a starting point to understanding
limits on distribution of species
Species absent
because
Yes
Area inaccessible
or insufficient time
Yes
Dispersal
limits
distribution?
Yes
No
Behavior
limits
distribution?
No
No
Biogeography & Distribution of Species
• Serves as a starting point to understanding
limits on distribution of species
Species absent
because
Yes
Area inaccessible
or insufficient time
Yes
Habitat selection
Dispersal
limits
distribution?
Yes
No
Behavior
limits
distribution?
No
Biotic factors
(other species)
limit
distribution?
No
Biogeography & Distribution of Species
• Serves as a starting point to understanding
limits on distribution of species
Species absent
because
Yes
Area inaccessible
or insufficient time
Yes
Habitat selection
Dispersal
limits
distribution?
Yes
No
Behavior
limits
distribution?
No
Biotic factors
(other species)
limit
distribution?
No
Predation, parasitism,
competition, disease
Abiotic factors
limit
distribution?
Biogeography & Distribution of Species
• Serves as a starting point to understanding
limits on distribution of species
Species absent
because
Yes
Dispersal
limits
distribution?
Area inaccessible
or insufficient time
Yes
Habitat selection
Yes
No
Behavior
limits
distribution?
No
Biotic factors
(other species)
limit
distribution?
No
Predation, parasitism,
competition, disease
Chemical
factors
Water
Oxygen
Salinity
pH
Soil nutrients, etc.
Abiotic factors
limit
distribution?
Physical
factors
Temperature
Light
Soil structure
Fire
Moisture, etc.
Hydrangea Flower Color
Hydrangea react to the
environment and ultimately
display their phenotype based
on the pH of their soil.
Hydrangea flower color is
affected by light and soil pH.
Soil pH exerts the main
influence on which color a
hydrangea plant will display.
17
Fish And Maintaining Homeostasis
In Various Water Conditions
Fish and other aquatic
animals deal with
changing
environments in part
due to nature and in
part due to human
interactions.
Pressure- their bladder fills with
gas to equalize internal pressure
18
Biogeographic Realms
19
Introduced Species
• What’s the big deal?
• These species are free from
predators, parasites and pathogens
that limit their populations in their
native habitats.
• These transplanted species
disrupt their new community by
preying on native organisms or
outcompeting them for
resources.
20
Guam: Brown Tree Snake
• The brown tree snake was
accidentally introduced to
Guam as a stowaway in
military cargo from other
parts of the South Pacific
after World War II.
• Since then, 12 species of
birds and 6 species of lizards
the snakes ate have become
extinct.
• Guam had no native snakes.
Dispersal of Brown Tree Snake
21
Southern U.S.: Kudzu Vine
• The Asian plant Kudzu was introduced by the U.S. Dept.
of Agriculture with good intentions.
• It was introduced from Japanese pavilion in the 1876
Centennial Exposition in Philadelphia.
• It was to help control erosion but has taken over large
areas of the landscape in the Southern U.S.
22
Introduced Species
23
New York: European Starling
• From the New York Times, 1990
The year was 1890 when an eccentric drug manufacturer named
Eugene Schieffelin entered New York City's Central Park and
released some 60 European starlings he had imported from England.
In 1891 he loosed 40 more. Schieffelin's motives were as romantic as
they were ill fated: he hoped to introduce into North America every
bird mentioned by Shakespeare.
Skylarks and song thrushes failed to thrive, but the enormity of his
success with starlings continues to haunt us. This centennial year is
worth observing as an object lesson in how even noble intentions can
lead to disaster when humanity meddles with nature.
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